High density magnetic recording medium has been developed yearly and the magnetic particles have changed from iron oxide type magnetic particles to metal magnetic particles. Magnetic recording medium using ferromagnetic metal particles has been widely commericialized as a compact cassette tape used in a fixed head type system, which is the so-called "metal cassette tape" for a metal position use.
Use of ferromagnetic metal particles enable one to select coercive force from a wider range, has larger magnetic moment than the conventional magnetic particles, and can be used widely for various purposes. Therefore it is beleived that in near future ferromagnetic metal particles are to be commericialized in various fields which requires high density recording.
Extensive studies have been made to provide a 8 mm video tape to be used in a rotary head type system, which is to be put into practical use in near future. Also, a digital audio tape (hereinafter referred to "DAT") by PCM recording has been studied.
DAT has strongly been desired as a tape for recording music with high efficiency, and it is believed that DAT is to be used in a wide range from high-fidelity recording to normal audio recording.
It is necessary that the magnetic recording medium can be used both in a rotary head type system and in a fixed head type system. Hitherto, magnetic recording medium used in the rotary head type system or in the fixed head type system have been separately developed.
A rotary head type system is mainly used for video recording, for example, in a VHS system or in Beta system. Generally, a smooth support is used and the surface of a magnetic layer is subjected to smoothing treatment in order to increase the recording density and to shorten the recording wavelength, which is disclosed in Japanese Patent Application (OPI) No. 143733/82 and 16243/83 (the term "OPI" as used herein means a "published unexamined Japanese Patent application"). However, when the magnetic recording medium having good surface smoothness is run in a fixed head type sytem, running disabilities such as tape squeal or running stop readily occur. It has been proposed that runnability can be improved by providing a backing layer on the opposite surface of the support to a magnetic layer. The use of such a backing layer is very costly.
A fixed head type system is used for normal audio tape, which is the so-called a compact cassette type for audio recording. The compact cassette tape is fabricated so that the recording wavelength is about 2 .mu.m or more and that running durability is sufficient enough to stand the use in a fixed head type system.
Therefore, the conventional tape has some problems in that the electromagnetic properties are not satisfactory in recording short wavelengths of 2 .mu.m or less and the running durability, i.e., still characteristic, is not satisfactory.
In the present invention, a magnetic recording medium of DAT which is suitable for high density recording and can be used both in a rotary head type system and in a fixed head type system has been developed.